Avalanche Forecast

Archived

Jan 5th, 2021–Jan 6th, 2021

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Northwest Inland.

Navigate around wind loaded slopes and keep in mind the potential for surprisingly large avalanches due to isolated weak layers.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

The windy storm continues until Wednesday afternoon.

TUESDAY NIGHT: Scattered flurries with localized accumulations of 5-10 cm, strong southwest wind, temperatures around -4 C.

WEDNESDAY: Flurries continue with another 5-10 cm of snow throughout the day, moderate to strong southwest wind, temperatures around -6 C.

THURSDAY: Partly cloudy, strong south wind, temperatures around -4 C.

FRIDAY: Partly cloudy, moderate south wind, temperatures around -6 C.

Avalanche Summary

Over the weekend there were several reports of natural size 1-2 slab avalanches in east-facing alpine terrain (see some photos here, here, and here). Most of the activity was on wind loaded slopes. Some large whumpfs were reported in the Babines. No persistent or deep persistent slab avalanches have been reported since Dec 22, however there is still potential to trigger large avalanches in steep rocky terrain.

Snowpack Summary

Strong to extreme wind is moving around 30-50 cm of snow that has fallen since New Year's Day. Thick wind slabs can be found in exposed open terrain, sheltered terrain should have mostly low density snow. However, isolated storm slabs could be forming on steep rolls in sheltered areas where recent snow may be settling above surface hoar.

The lower snowpack has two crusts with potentially weak snow around them. One is 60-90 cm below the surface and the other is near the ground. These layers produced avalanches on Dec 21 and 22, but since then have been trending towards dormancy. We are uncertain about how likely it is to trigger avalanches on these deeper layers, but would be most suspect of shallow rocky slopes in the alpine.

Terrain and Travel

Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
Choose slopes that are well supported and have limited consequence.
Be especially cautious near rock outcroppings, on steep convexities and anywhere the snowpack feels thinner than average.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.